Tinea nigra is a rare infection of the fungi. This causes the emergence of brown or black patches on foot soles, hand palms, or, on rare occasions, abdomen.
A form of yeast called Hortaea werneckii causes most infections with tinea nigra. A person may get the infection, often through a small wound, when the yeast gets into their body.
Read on to learn more about an infection with tinea nigra, including the symptoms, diagnosis and treatment options.
Tinea nigra causes patches of brown or black to appear on the soles of the feet or hand palms. The patches may be so small and weak as not to be seen by a individual. Also, they tend to grow gradually. The signs most prevalent include:
- a patch on the foot or hand following an injury
- a single round, linear, or irregularly shaped patch that grows slowly
- growing patches that either cause no symptoms or itch
- patches that resemble a growing mole or freckle
- a slow growing brown patch on the torso
The infection affects people living in tropical regions and those who have traveled to these areas recently.
Most people with tinea nigra suffer from one lesion only. However, if the fungus comes into contact with multiple entry points, such as wounds on both hands, a individual could have several patches.
Tinea nigra, in healthy people, exists only on the skin’s superficial layers. It does not spread, cause severe infections or pose significant health risks. It is more likely to affect youngsters under 20 years of age.
Tinea nigra is a fungal infection which means that when a person comes into contact with a fungus that can cause the infection, they get it.
Hortaea werneckii used to be called by scientists either Cladosporium werneckii, Exophiala werneckii or Phaeoannellomyces werneckii. Another yeast called Stenella araguata can cause tinea nigra in some cases.
As with many other fungi, Hortaea werneckii thrives in moist or humid environments. It lives on dead and decaying organic material, such as soil and wood. It can get into the human body when it comes into contact with the skin, usually through a wound. It is most likely to live on parts of the body with many sweat glands, such as the hands and feet.
Certain risk factors increase a person’s likelihood of developing this infection. They include:
- living in a tropical or subtropical region
- recent travel to a subtropical or tropical region
- a history of hyperhidrosis, a condition that causes excessive sweating
- a recent injury
- contact with wood, soil, or compost, such as from gardening without gloves or woodworking in a tropical or subtropical region
Symptoms of a person can often lead a doctor to suspect tinea nigra. However, as tinea nigra can mimic the symptoms of a variety of other conditions, accurate diagnosis is important.
The doctor can ask the patient about their recent history of travel, injury and exposure to wood, compost, or soil. Normally, they will also take a skin culture and send it to a lab to see if Hortaea werneckii can develop within a week. If it does, that means the test for tinea nigra is positive.
A doctor may also often perform a skin biopsy to test for skin cancer, since certain forms of skin cancer may look similar to tinea nigra.
People who want to try remedies from home may see improvements with keratolytic agents. A keratolytic is a chemical that assists in removing excess skin. Some keratolytics which are potentially successful include:
- wart cream
- salicylic acid
- Whitfield’s ointment
In pregnancy, such medications may not be safe and women who are pregnant or planning to become pregnant should see a doctor instead of attempting home remedies.
When home care fails, it would be easier to see a doctor. Other possible causes of brown skin lesions.
Doctors usually recommend antifungal topical creams for treating tinea nigra. As a doctor advises people should apply the cream directly to the patch.
A person may also need to take oral antifungal medications in some situations, particularly if the lesions are very large or if antifungal creams have not worked. Oral medications may be unsuccessful though.
Doctors don’t know which length of treatment is best, but one report’s authors suggest that 1 month of treatment is enough.
People can reduce the risk of tinea nigra infections by protecting the skin from exposure to soil, compost, and other materials in which the Hortaea werneckii fungus likes to grow. Following this advice is especially important for people who travel to or live in tropical regions.
These strategies can help:
- practicing frequent handwashing, especially after spending time outside
- wearing gloves or other protective gear in the garden
- refraining from walking outside with bare feet
- wearing socks or shoes in public places
- changing socks frequently, especially if they get wet
- covering any wounds on the hands or feet before spending time outside
Several other skin conditions can look tinea-nigra-like. Other fungal infections, such as foot of an athlete, may also cause skin lesions, but they are typically not brown.
Melanoma, a type of skin cancer, can be fatal. In the early stages it can also look very similar to tinea nigra. Melanoma is not usually painful at first, much like tinea nigra. Hence, people who are not getting relief from home or medical treatment should see a dermatologist and ask for a biopsy.
Some other medical conditions and factors which could cause brown patches include:
- skin staining from henna
- skin hyperpigmentation from pregnancy or Addison’s disease
- complications of syphilis
- exposure to certain chemicals, such as silver nitrate
Tinea nigra does not constitute a serious medical condition. The majority of people report no signs other than brown spots on the skin.
However, it is necessary to see a doctor for an accurate diagnosis as tinea nigra looks similar to several other conditions.
Prompt care will prevent serious skin conditions from worsening.